The general field of the present invention is a high voltage actuated multiple flashlamp system utilizing a high voltage low energy electrical power source to ignite the flashlamps in sequence. Said multiple flashlamp system can be of the planar array type which is provided with plug-in connector tabs at each end of the unit to fit into the socket of a camera. Such flash lamp unit can be provided with an upper array of flashlamps which are electrically connected to a lower plug-in tab by means of an associated electrical circuit board so that only the upper lamps in the array will be flashed when the lower tab has been inserted into the camera socket. By turning the flashlamp unit top to bottom and reinserting the remaining tab in the camera socket, it becomes possible to flash a second group of flashlamps which are now oriented farthest away from the axis of the camera lens. This is made possible by means of a different circuit path on the associated circuitboard which electrically interconnects said lamps with the connector tab now inserted in the camera socket. The above generally described lamp sequencing arrangement eliminates or reduces the undesirable "red-eye" effect since only the lamps of the array that can flash are grouped relatively farthest from the axis of the camera lens.
The already known high voltage type flashlamps employed in such multiple flashlamp systems require a short duration pulse of approximately 1,000 or 2,000 volts at a low current value. Although the firing pulse is sometimes called a "voltage pulse", it is primarily the energy of the pulse, comprising the combination of voltage, current and time duration, that causes an individual lamp to flash when a firing pulse is applied across the spaced apart inleads of an unflashed lamp in the circuit. The firing pulse source may comprise a suitable battery-capacitor discharge and voltage step-up transformer type of circuit, or may employ a compact piezoelectric element arranged to be impacted or stressed in synchronization with opening of the camera shutter, so as to produce a firing pulse with a voltage of approximately 1,000 or 2,000 volts and of sufficient energy to fire a single flash lamp. An example of a high voltage flashlamp and a firing pulse source comprising a piezoelectric element synchronized with the camera shutter is described in U.S. Pat. Nos. 2,972,937 and 3,106,080, both to C. G. Suits.
A flashlamp construction of the all glass type that can be actuated by a high voltage pulse in the above described type multiple photoflash lamp systems further contains a combustion-supporting gas such as oxygen within a hermetically sealed glass envelope together with a loosely distributed filling of a suitable light producing combustible material such as shredded foil of zirconium, aluminum or hafnium, for example, which upon ignition produces a high intensity flash of actinic light. In typical high voltage flashlamp constructions, a fulminating type primer material is employed as a mass electrically connected directly across and between a pair of inlead wires extending into the lamp glass envelope. The primer material may be positioned and carried in the lamp on top of a glass or ceramic insulating member through which the inlead wires extend, or may be carried in a cavity provided in such a member. Ignition of said primer material responsive to the firing pulse desirably provides a sufficient blast that the inleads remain spaced apart in an open circuit condition. The known primer materials for such flashlamp constructions also desirably produce a non-conductive residue upon combustion to further help avoid establishing any low resistance shorting path between the spaced apart inleads after the lamp has been flashed.
A known primer material of this type which is disclosed in the above referenced patent application Ser. No. 508,107 comprises a solid mixture of a combustible fuel and an oxidizer for the fuel such as alkaline metal chlorates and perchlorates, and which further contains a combustion-supporting oxide of the type which is converted to a lower oxide upon combustion of the mixture. Combustion-supporting oxides already found suitable in the primer material can be selected from the group consisting of Co.sub.3 O.sub.4, BaCrO.sub.4, Fe.sub.2 O.sub.3, and higher oxides of nickel by reason of not converting to form a conductive residue after the primer has been ignited. In contrast thereto, other metal oxides found not suitable include CuO, PbO, SnO.sub.2, TiO.sub.2 and ZnO which are said to form conductive residues hence have proven unsatisfactory for an "open circuit" type lamp construction.